Research On Technologies Of Hydrogen-contained Combustion With Dilution In Gas Turbines

The hydrogen-contained gas turbine combustion can be widely applied in industrial fields such as Integrated Gasification Combined Cycle (IGCC), Refinery, Chemical Engineering, and so on. Its related research is one of the key branches of gas turbine technology innovations. Currently, the diluted diffusion combustion is playing a crucial role on the design of hydrogen-contained gas turbine combustors with low emissions. The diluted diffusion combustion technologies of gas turbine combustors with high operating conditions or hydrogen-rich fuels need to be further studied. Based on the research objects, the whole dissertation can be divided into three parts:1. Fundamental research based on counterflow flames.First, based on the working principles of diffusion combustors, the concept of ’Equivalent Dilution Rate’ was properly defined. Then, simulations of diluted diffusion flames of CH4, syngas and H2 were carried out. The results show that there are negligible differences in the flame structure, NO production routes or rates between air side dilution and fuel side dilution. Most of the NO in syngas flames is due to both the thermal NO and some NO comes from the NNH route; while almost all the NO in H2 flames comes from the thermal NO. The maximum temperature of syngas and H2 flames can be reduced significantly by N2 dilution, which reduces the production rate of the thermal NO. It is the primary factor of the decrease of the total NO production rate.2. Technology-research based on a combustor modelA simplified combustor model was proposed and a hydrogen-contained fuel nozzle was designed. Diluted diffusion combustion technologies of both H2 and syngas were studied separately. A new N2 injection design, injecting N2 from the middle of the combustor, was proposed for the syngas combustor. It not only reduces the NO emission but also addresses the distorted-air-distribution problem, increases the flame stability. Besides, the results show that the design allows a further increment quantity of N2 injection, which brings the possibility of achieving an ultra-low NO emission. Since the flame could be held on the surface of the fuel nozzle if N2 dilutes air, N2 has to dilute the fuel in the H2 combustor.According to the results of numerical and experimental studies, the reduction of total NO production rate in both combustors is dominated by the reduction of thermal NO production rate of air injection zone and post flame zone in the combustion chambers. As the dilution rate increases, the NO emission will decrease significantly. For the syngas combustor, the NO emission is 10ppm@15%O2 when the dilution rate is 50%; while the NO emissions with different equivalence ratios (0.33-0.47) are all less than 25ppm@15%O2 when the dilution rate of H2 combustor is 60%.3. Test based on a real combustorThe N2 injection design of the simplified syngas combustor was introduced into the design of a real syngas combustor. The test results indicate that the combustor is able to operate smoothly and safely in a wide range of loads; the NO emission is less than 25ppm@15%O2 in its design condition, which proves the validity of the design.